Man page 3 : XkbOpenDisplay

XkbOpenDisplay - Checks for a compatible version of the Xkb extension in both the library and the server, and initializes the extension for use.

Display XkbOpenDisplay (char * display_name , int * event_rtrn , int * error_rtrn , int * major_in_out , int * minor_in_out , int * reason_rtrn );

• display_name
      hardware display name, which determines the display and communications domain to be used
• event_rtrn
      backfilled with the extension base event code
• error_rtrn
      backfilled with the extension base error code
• major_in_out
      compile time lib major version in, server major version out
• minor_in_out
      compile time lib min version in, server minor version out
• reason_rtrn
      backfilled with a status code

As a convenience, you can use the function XkbOpenDisplayto perform these three tasks at once: open a connection to an X server, check for a compatible version of the Xkb extension in both the library and the server, and initialize the extension for use. XkbOpenDisplayis a convenience function that opens an X display connection and initializes the X keyboard extension. In all cases, upon return reason_rtrncontains a status value indicating success or the type of failure. If major_in_outand minor_in_outare not NULL, XkbOpenDisplayfirst calls XkbLibraryVersionto determine whether the client library is compatible, passing it the values pointed to by major_in_out andminor_in_out. If the library isincompatible, XkbOpenDisplay backfillsmajor_in_outand minor_in_outwith the major and minor extension versions of the library being used and returns NULL. If the library is compatible, XkbOpenDisplaynext calls XOpenDisplaywith the display_name.If this fails, the function returns NULL. If successful, XkbOpenDisplaycalls XkbQueryExtensionand backfills the major and minor Xkb server extension version numbers in major_in_out andminor_in_out. If the serverextension version is not compatible with the library extension version or if the server extension is not present, XkbOpenDisplaycloses the display and returns NULL. When successful, the function returns the display connection. The possible values for reason_rtrn are:

5 XkbOD_BadLibraryVersion indicates XkbLibraryVersion returned False.

5 XkbOD_ConnectionRefused indicates the display could not be opened.

5 XkbOD_BadServerVersion indicates the library and the server have incompatible extension versions.

5 XkbOD_NonXkbServer indicates the extension is not present in the X server.

5 XkbOD_Success indicates that the function succeeded.

• NULL
                 The XkbOpenDisplayfunction returns NULL if the library is incompatible.
  
  The XkbOpenDisplayfunction returns NULL if the call to XOpenDisplaywith the display_namefails.
  
  The XkbOpenDisplayfunction returns NULL and closes the display if the server extension version is not compatible with the library extension version or if the server extension is not present.

• BadAccess
                 The Xkb extension has not been properly initialized

R XkbLibraryVersion (3),

R XkbQueryExtension (3),

R XOpenDisplay (3)